Scientific researchers in Berlin have proposed (verified numerically) a method for using optical pulses to change the intensity of other optical pulses by interacting with each other at an optical event horizon. Optical switching is typically done in a "mechanical" way by changing the properties of the fiber medium. Performing the switching optically usually requires a very strong control pulse (as colliding pulses do not change much), but the new proposed method states it can be done with a control pulse that is 7 times weaker than the central wavelength. The proposal meets the requirements set forth for an useful, all optical transistor, which could lead to purely optical circuits. You can read their proposal The American Physical Society's Website or a summarized write up at Physorg.com This proposal was submitted to the APS in November of 2010, and published last month.